Method of removing high molecular weight naphthenic acids from hydrocarbon oils



L HERCE ETAL Filed Feb. 6, 1956 METHOD OF REMOVING HIGH MOLECULAR WEIGHTNAPHTHENIC ACIDS FROM HYDROCARBON OILS Sept, 2, 1958 3 WEEK? 5 .EwnEmzwznpim z 7 NO QEAGWELXE "NM 8&6!

JNVENTORS WILLIAM L. FIERCE GEORGE M. LONGLANQJ ATTORNEY United StatesPatent O-"ice ll/IETHOD 01* REMfii/ING HIGH MOLECULAR WEIGHT NAPHTIENKIACES FRQM HYDRO- CARBON OILS William L. Fierce, Crystal Lake, 311., andGeorge M. Longland, J12, Harrisburg, Pa., assignors to The lfure OilCompany, Chicago, 111., a corporation of Ohio Application February 6,1956, Serial No. 563,470

16 Claims. (Cl. 196-41) This invention relates to a method and a newsolvent combination for the extraction of high molecular weightnaphthenic acids from hydrocarbon mixtures and, particularly, from lightto residual lubricating stocks or solvent extracts from the solventextraction of lubricating oil. The acidic constituents extracted bymeans of this invention are broadly classifiable as naphthenic acidswhich, at least in part, are characterized as being high molecularweight carboxylic acids which are liquid or solids and being aliphaticacids and alicyclic acids having above about 25 carbon atoms to themolecule, showing little or no unsaturation and consisting essentiallyof cyclic acids and polycyclic acids. These acidic materials generallyboil above about 600 F. and because of their high molecular Weight ofierdifiiculty in their removal from lubricating oils for the purpose ofproducing finished lubricating oils of low acid number.

It has been found that, contrary to the teachings of the prior art,there is a distinction between the extraction efiiciencies to be gainedby the use of various solvent compositions to extract naphthenic acidsfrom lubricating oil fractions. In accordance with this invention, ithas been found that although ammonia alone or methyl alcohol alone ortheir combination with water is not a satisfactory solvent fornaphthenic acids in lubricating oils, a mixture consisting of methylalcohol and from about 5.0 to 7.0 wt. percent of ammonia in anhydrouscondition, or containing no more than about 0.4 wt. per-.

cent of water, is an efiicient medium for this purpose. This discoveryis based on experience with a vast number of solvent combinations usedto treat various lubricating oils containing naphthenic acids ofdifierent molecular sizes and under varying conditions of extraction. Inaddition, it has been found that the application of certain extractionconditions of temperature and pressure using anhydrous methyl alcoholand ammonia greatly increases the degree of removal of all acidiccompounds present and classifiable as naphthenic acids whether the oilbeing treated contains a predominance of those naphthenic acids whichare difiicult to extract or not. The concentration of ammonia betweenthe range of 5.0 to 7.0 wt. percent is calculated to include suificientammonia to at least neutralize the naphthenic acids present in the oilsbeing treated and provide for at least some excess over stoichiometricrequirements for this purpose.

The invention, therefore, has as its primary purpose that of providing amethod and solvent composition for extracting naphthenic acids fromhydrocarbon mixtures, particularly lubricating oil fractions andresiduums.

Another purpose of the invention is to provide a solvent compositioncontaining methyl alcohol and between about 5 to 7 wt. percent ofammonia with no more than about 0.4 wt. percent of water and preferablya solvent composition which is substantially anhydrous. Accordingly,although the invention and the problem solved by it will be described byreference to particular lubricating oil fractions and the reduction ofthe acid number thereof, the illustrations given are not to be construedas limita- 2,850,435 Patented Sept. 2, T958 lubricating oil stocks tochemical and physical treatments in order to improve the viscositycharacteristics, low temperature fluidity, oxidation stability, andlower the carbon residue, sulfur content, and neutralization values inorder that the requirements of modern lubrication may be met by thelubricating oils. One problem that has faced the refiner of lubricatingoils is the removal of acidic constitutents from the heavy or residuallubricating oil stocks, as for example, preparing such lubricating oilshaving low acid numbers as determined by ASTM D974- SZT. As the refiningoperations of dewaxing, deasphalting, and solvent refining exert theirinfluences upon the lubricating oil fractions, the acidic constituentsremaining become much more difficult to remove. Refiners have in thepast applied various solvent extraction methods employing dilute aqueousalkali solutions and Various organic solvents in their effort to producelubricating oils having acceptable neutralization values. Aqueous andanhydrous ammonia solutions have been used, followed by alcoholextractions, to remove the deleterious naphthenic acids. Aqueous ammoniasolutions in combination with emulsion breakers, such as methyl alcohol,ethyl alcohol, or acetone, have been applied in various extractionprocesses in an efiort to finish lubricating oils for use with variousadditives that have become necessary to meet the extreme conditions inmodern lubrication. In spite of the prior art efforts, in many instancesthe persistence of acidic constituents or naphthenic acids in finishedlubricants has proved detrimental.

For instance, it is known that about 99 percent of the lower boilingnaphthenic acids may be removed from light lubricating oil distillates,which may have an acid number in the range of 2 to 3, by treatment withrelatively dilute aqueous alkali solutions. The treatment of a lightlube distillate having an acid number of 2.75 with an equal volume of 5percent aqueous potassium hydroxide removes about 99 percent of thenaphthenic acids. Treatment of the same distillate with 1.0 N ammoniumhydroxide will remove about 89 percent of the acids. The heavierlubricating oil distillate and heavy bottoms or residues aforementioned,after dewaxing or deasphalting, contain certain complex and/or highmolecular weight naphthenic acids which are increasingly diflicult toremove. To illustrate, a deasphalted hydrocarbon oil havmg an acidnumber of 1.75 on treatment with an equal volume of 1.0 N ammoniumhydroxide results in the removal of only 23 percent of the acids. Thissame oil treated with a solvent comprising one part of 5.0 percentaqueous potassium hydroxide and one part of Formula 30 alcohol resultsin the removal of only 1.8 percent of the naphthenic acids. Treatment ofthis same deasphalted oil with a solvent comprising 3 parts of 1.0 Nammonium hydroxide, 2 parts of l-butanol, and 2 parts of 2-propanolaccomplishes the removal of about 76 percent of the naphthenic acids.

Proceeding further with the refining, it is found that the acid numbersof some deasphalted products before solvent extraction may be in theorder of 1.0 to 2.5. Subsequent removal of waxy hydrocarbons andresinous materials in the final stages of refining to produce finishedlubricating oil blending stocks, such as the bright stockaforementionei'has the ell'ect of further reduction of the acid numberto values ranging from 0.3 to 1.0. Such stocks as residues, dewaxedbright stock, solvent extracts, and heavy lubricating oil distillatescontain naphthenic' acids of higher molecular weight or complexity whichcannot be successfully removed by the application of prior art sOiVents.For example, treatment of a dewaxed bright stock with the ammoniac'albutanolpropanol solvent aforementioned results in the extraction.

, temperature.

was conducted which points to the fact that anhydrous ammonia-methanolsolvent compositions are superior to the use of either component alone,whether or not water is present, and also superior to the expectedsolvent action from a combination of the two components with very smallamounts of water. Most of the extractions in this series were carriedout in glass separatory funnels at room The two phases were mixedthoroughly and then allowed to separate completely. The lower,

solvent-rich phase was carefully withdrawn and the volumes of the twophases were noted. The naphthenic acid content of each phase wasdetermined by the ASTM 13974-521 method. The solvent was stripped fromboth phases to yield the extracted oil and the recovered, semipurenaphthenic acids. in experiment 2 the solvent was anhydrous ammonia.This extraction was made in a closed ierguson gauge at room temperatureat a slightly elevated pressure.

Table I NAPHTHENIO ACID SOLVENT EXTRACTION DATA Solvent volume .=1,temperature=75 F] oil volume Solvent composition (volume percent)Oilrecovery Oil treated K 1 vol.

Ammo- Water Metha- 2-propa- Butanol percent) nia 1101 1101 (1) Phenolextract from 85 distill e 0. 61 94. 8 (2) Phenol extract from 8 late0.16' 1 99. (3) Pheno1 extract irom 85 distillate 5. 46 93. 2 (4) Phenolextract from 170 distil- 2.16 95. 7 (5) Phenol extract from 170 distil-1.5 4.5 94 -r. 1.07 96.2 (6) Phenol extract from 170 distil- 0.5 1.5 4949 4.00 91.2 (7) Phenol extract from 170 distil- 0.5 1.5 1.59 76.0 (8)170 distillate 0. 48 98. 9 (9) 170 distillate 0.6 2. 4 l4. 1 96. 6 (10)170 distillate 0. 6 2. 4 3. 09 85. 7 (11) 170 disti11ate 0.8 18. 6 10. 697.0 (12) 170 distillate... 4.0 41.0 96. 5 (13) 170 distil1ate 0. 2 0. 59. 9 96. 4 (14) 170 distillate 0.4 1. 2 13. 1 96. 2 (15) 170 distillate0. 6 l. 8 13. 9 96. 8 (16) DAO 3 0. 8 2. 4 2. 91 98. 2 (17) DAO 0.8 2. 42.10 94. 4 (18) DAO 0. 8 2. 4 l. 91 96. 6 (19) DAO 0. 8 2.4 2. 71 86.3(20) 80 distillate p 4.0 96.0 60.0 97. 0

1 Ooncentration of acids in extract 1 Estim Concentration of acids inrafiinate' ated 3 Deasphalted oil was diluted with approximately hexaneby volume.

refining practice. Furthermore, it is desirable that the extraction beeasily manipulated, produce the greatest possible reduction in acidnumber, and allow the purification of the naphthenic acids which inthemselves represent a valuable product. Since refining methods difiergreatly in their ability to remove naphthenic acids but may induce otherdesirable changes in the hydrocarbon mixtures treated, it is alsoessential that any methods applied to meet aparticular acid numberrequirement are easily coordinated with the established refiningmethods.

In order to demonstrate the present discovery of a solvent compositionwhich strikes. a balance between selectivity and miscibility wherebyboth low and high molecular weight naphthenic' acids, the latter beingordinarily difl-lcult to'remove from lubricating oils, are ef fectivelyremoved, a series of batch, equilibrium, continuous and pilot plantexperiments are described.

NAPHTHENIC ACID RECOVERY-ONE STAGE TREATMENT In order to demonstrate theeffectiveness of this solvent, a series of one-stage, low temperatureextractions than the distillate itself since the extractscontain a muchhigher naphthenic acid content than the original distillates. Even so,an examination of experiments 1 and 8 using methanol shows that thissolvent is unsatisfactory. A'mmonia, alone (experiment 2) gives evenmore unsatisfactory results in comparison with methanol (experiment 1)on the same type of oil. Experiment 3 shows that 0.25% ammonia, 0.75%water and 99% methanol gives an increased K value, or extractionefficiency, but the oil. recovery is lowered and consequently the purityof the acids extracted is diminished. Comparison of. experiments 4, 6and 7 shows that replacement of part of the methanol in the solvent with-2-propanol increased the extraction efiiciency but again loweredthepurity of the acids, whereupon replacement'of all of the methanolwith 2-propanol (experiment 7) reduced both the extraction efiiciencyand acid purity.

Considering next the experiments 8 through 15 on the treatment of visdistillate lubricating. oil fractions, it is seen that the highestextraction efliciency without appreciable sacrifice of naphthenic acidpurity or oil loss was obtained in experiment 12 using 4.0% ammonia with96.0% methanol. In experiment the change from methanol to 2-propano-lgreatly reduced the extraction efliciency and lowered the naphthenicacid purity from that obtained in experiment 9, using the same amountsof water and ammonia in each case. Increasing the ammonia and watercontent of the 2-propanol solvent in experiment 11 did not recover thelost efficiency but did increase the product purity. According toexperiments 13, 14, and 15, increase in water content with increase inammonia content, using methanol, had very little effect on thenaphthenic acid purity and seemed to favorably influence the extractionefficiency; but, leaving the water out entirely (experiment 12) gave atremendous increase in extraction efliciency with little or no loss innaphtbenic acid purity.

The naphthem'c acids present in lubricating oil fractions ofMid-Continent origin will vary in molecular weight from about 350 to550. The ease of extraction decreases with increase in molecular weightof the acids, depending on the concentration of the naphthenic acids inthe oil being treated. This is demonstrated in part by comparison ofexperiment 20 with experiment 12 (Table I). The 80 vis. distillatecontains naphthenic acids varying in molecular weight from 352 to 363.The 170 vis. distillate contains naphthenic acids of molecular weightequipped with supplementary heaters. All components charged to and takenfrom the bombs were carefully weighed both in the charge or productcontainer used in the transfer and in the bombs. The volumes were alsorecorded to serve as another check on the weights. The oil-acid mixturewas charged first, after which the bomb and solvent were chilled toprevent ammonia loss during solvent addition. After the charge had beenadded, the bomb was placed in the bath for an hour with vigorous shakingeach five minutes, after which it was inverted and placed in the bathwith the inlet valve and line submerged for a half hour settling period.Following this settling period, the lower oil phase was carefullywithdrawn, first into a beaker, and later as the interface approached,into a graduated cylinder. The bomb was then returned to the bath foranother half hour period to prevent contamination of the acid phase withoil clinging to the sides of the vessel. A small amount of acid phasewas then withdrawn into the graduated cylinder and the remainder chargedto a glass distillation flask. Weights and volumes were recorded foreach phase after which the solvent was stripped from the samples in thebeaker and distillation flask. Neutralization values, in accordance withASTM Method D974-53T (1948 N. N.), were used as a measure of acidcontent of the charge and products. The results are shown in Table II.

Table 11 SUMMARY OF DATA FROM EQUILIBRIUM EXPERIMENTS NAPHTHENIO ACIDEXTRACTION FROM DEASPHALTED OIL Charge oil I Solvent Oil phase Acidphase Treat- Exp. No. Weight Weight Weight Weight Total g Weight 1948Weight 1948 Weight 1948 Weight percent percent percent percent weight (0percent N. N. percent N. N. (EUL) N. (gm.) arnmethwater l-bu- (grams)s01. rec. oil sol. rec. acid acid monia anol tanol 1. 51 237. O 5. 9 94.1 108. 1 170 5. 4 0. 76 94. 9 34. 2 4. 7 1. 51 122. 0 5. 9 94. 1 212. 1170 3. O 0. 46 97. 8 26. 9 4. 4 1. 51 184. 2 5. 9 94. l 166. 6 170 4. 30. 58 97. 0 37. 3 3. 5 1. 48 184.0 9.8 91. 2 157. 2 170 3. 6 0. 65 96. 936.0 4. 4 1. 52 187. 7 2. 1 97. 9 160. 0 170 2. 3 0. 66 97. 1 35. 8 4.5 1. 52 188. 6 8. 0 92.0 163. 4 195 6.0 0. 67 97. 3 38. 4 4. 0 1. 51184. 8 5. 8 94.2 158. 4 140 4. 6 0.64 95. 5 24. 0 6. 8 1. 5 184. 5 9. 870. 2 154. 8 140 2. 9 0. 81 96. 7 27. 0 4. 7 0. 181. 9 5. 9 94.1 166.1170 2. 4 0. 18 96.5 0.83 5. 6 0. 116. 7 6. 2 93. 8 119. 2 170 6. 5 0. 2097. 3 2. 95 2. 7 0. 20 184. 4 9. 8 91. 2 167. 0 170 2. 6 O. 18 98.5 8.01 2. 3 0. 20 182. 6 2. 1 97. 9 158. 8 170 2. 5 0. 18 97. 4 2. 69 4.00.20 183. 5 8.0 92.0 162.0 195 0. 9 0.18 98. 3 4. 66 2. 5 0. 19 190. 26. 1 93. 9 160.0 140 4. 0 0.19 96.8 2. 23 4. 9 0.19 183. 1 9.8 90. 2156. 2 140 7.0 0. 19 97.3 2. 6 3. 5 1. 51 187. 3 5. 9 91. 1 162. 4 1703.6 0. 68 97.5 40. 6 3. 9 1.51 181.0 5. 9 82. 1 167. 0 170 3. 3 0.95 97.8 27. 7 3. 8 1. 52 284. 9 5. 7 94. 0 158. 1 170 2. 8 0. 97. 8 46. 1 3. 20.20 184. 9 4.8 75. 6 165. 4 170 3. 6 0. 18 98.3 3. 90 2. 5 1. 52 185. 25. 8 18. 8 161. 2 170 15. 8 0. 64 82. 5 6. 49 25.0 35. 8 194. 6 6.0 94.0 162. 2 170 7. 67 13. 3 69. 12 7S. 2 63. 3 55. 4 188. 3 5. 9 94.1 157.7 170 14. 7 24.6 48. 3 61. 3 144. 4

1 Charge oils with 1948 neut. nos. of about 1.5 were ordinary DAO. Othercharge oils were prepared by addition or substitution of pilot plantnaphthenic acids or extracted oils.

around 427. Substantially complete removal of naphthenic acids of lowmolecular weight is efiected in one stage treatment of the 80 visdistillate as compared with the 170 vis. distillate. Experiments 16through 19 represent the results obtained in treating a deasphalted oil(diluted with 25 vol. percent of hexane to reduce the viscosity). Kvalues of about 2.0 to 3.0 are considered excellent for this type ofoil, but the phase separation was slow and the neutralization value ofthe finished oil did not meet standard requirements. This was attributedto the presence of the 2.4% of water in the solvent composition as willbe demonstrated.

NAPHTHENIC ACID RECOVERY-EQUILIBRIUM DATA In experiments 23, 22 and 21at 170 F. the effect of varying the solvent/ oil ratio was studied. Itcan be seen that the neutralization number reduction of the oil wasdirectly proportional to the ratio, while the purity and yield of therecoveredo acids were roughly inversely proportional to the ratio.Experiments 23, 24 and 25 indicate the effect of varying the ammoniaconcentration in the solvent. The neutralization number reduction of theoil was better with 5.9 wt. percent ammonia than with either 9.8 or 2.1wt. percent. Yet it should be noted that the extraction was quiteeflicient at all three ammonia levels. Experiments 26, 27 and 28 showthe effects of carrying out the extractions at temperatures other than170 F. The results at and 195 F. were inferior to those obtained at F. Acomparison of experiments 27 and 28 indicates that better results areobtained with 5.8% ammonia in the solvent than with 9.8%. This periments23 and 24.

Inexperiments'29, 30, 31, 32, 33, 34 and 35 thecharge oil was apreviously extracted deasphalted oil. The results indicate that it isquite difiicult to reduce the neu- 8 Table IV tralization number of theoil below about 0.18 in any source 80 dist, 170 ($350 dist 15051 stageextraction regardless of the conditions used. The efle'ct of water uponthe extraction of naphthenic acids is clearly brought out by experiments36, 37 and 38, of F gTavigy 1149 Table 1- These data are presentedgraphicauy in asset ditiiiiii? :3: i933? iifiii i333; "i215 ure I; Shallamounts of water up to about 0.4 wt. per- Percent g fi acent can betolerated. However, the extraction eficiency ig? i' i ib?" qu1ckly dropsofi as the Water content of the solvent is M01. Weight ofuilfe acids-363 427 455 54% increased. Experiments 39 and 40 indicate that somel-butanol can be tolerated in the solvent. However, as ASTM DISTH'LATIONthe amount increases the selectivity of the solvent decreases with alesseningin neutralization number reduc- 15 Source 5% 40% %7- EPtion'and a decrease in the purity of the recovered naphthenic acids.Experiments 41 and 42 indicate that ef- 92% 2 3 g; 525 fe'ctiveextractions of deasphalted oil can be made even 760 l 925 945 whenexcessive amounts of'acids are present. 920 950 11085 1 The equilibriumexperiments were designed to study the efiects of the followingvariables: temperature, ammonia, concentration, solvent/oil ratio, waterconcentration, and the use of alcohols other than methanol. It was foundthat the most efiicient solvent is one composed of 6% by wt. of ammoniain methanol. 'Any increase or decrese in the ammonia percentage oraddition of water or butanol to the solvent caused a marked decrease inextraction efiiciency. Using a weight relationship of about 42.1 grns.of deasphalted oil to 38.1 gms. of solvent, containing- 6.2% by wt. ofammonia and 93.8% by wt. of methanol, at 170. F. produced the greatestreduction in naphthenic acid content for deasphalted oil containingthose. acids most. difi'jcultto extract. Obviously, the acid purity canbe increased by re-extraction, using a continuous tower operation. Acidpurities of 80% or higher'are predictable. I

Specific information as to theetiect. of various variables. upon theextraction of deasphalted oil is contained in Table II. V

In order to demonstrate the superiority of the anhydrous V 40ammonia-methanol solvent in treating all types of distillates, a seriesof equilibrium experiments were conducted like those shownv in Table Husing various distillate oils either in their pristine condition or withadded quantities of naphthenic acids obtained from pilot plantextractions of other distillates. These experiments were all conductedusing a solvent comprising 6.1% by wt. of ammonia and 93.9% by wt. ofmethanol. The results which 7 are shown in Table III indicate that thissolvent is highly effective for the extraction of naphthenic acids fromthe distillate oils.

Table III It is preferable to carry out the extractions at temperaturessufiiciently elevated to' preclude any necessity fordiluents, but if lowtreating temperatures (80110 F.) are used, dilution of the oil to betreated with hexane or carbon tetrachloride to reduce its viscositygives improved results. The lubricating oil fractions usedin the experiments were of Mid-Continent origin. The term 80 Dist. means that thedistillate oil has a viscosity of 80 SUS at F. The same connotationapplies to the terms 170 Dist. and350 Dist. The viscosity of the brightstock is measured at 210 F., i. e., 150 SUSbright stock at 210 F. Thisbright stock was derived from the deasphalted oil used in the previousexperimentsby dewaxing, which step is unnecessary before the naphthenicacids can be fractionated therefrom. i

The process and solvent composition 01; this invention is particularlyapplicable to continuous extraction techniques whereby the oil tobe-treated is passed into the top of an extractiontower wherein it meetsthe stream of upwardly flowing solvent. The extract solution is taken onat the top of the tower and the ratfinate solution is drawn ofi from thebottom thereof. To demonstrate this aspect of the invention, a series'ofexperiments was conducted in a pilot plant designed to carry out continuous counter-current solvent extraction. Since the details of suchprocesses are well known in the art, only a general description. of theapparatus is necessary to describe the experiments, the results of whichare shown in Table V. p

In carrying out these continuous counter-current extraction experiments,a treatingltower. consisting of twenty- SUMIMARY OF DATA FROMEQUILIBRIULI EXPERIIVIENTS NAPHTHENIG ACID EXTRACTION FROM LUBEDISTILLATES Charge oil Oil phase Acid phase Sol- Treat- Exp. vent, ing N0. total temp. Weight 1948 Weight 1948 Weight Stock 1948 Weight weightF.) percent N. N. percent N. N. (gm) N. N. (gm.) (grams) solventrecorgsred solvent rec. acid acid 43 2. 58 192. 4 79. 6 1. 7 0.22 88.659. 3 9. 1 44---- 31. 9 196. 8 77.6 140 3. 8 5. 95 53.3 94.8 58.0 45 17.4 188. 5 78. 9 140 2. 5 2. 10 71. 6 104. 0 27. 6 2. 91 193. 8 80. 4 v 1.9 0. 44 89. 2 55. 9 8. 7' 4 40. 0 194. 9 79. 9 150 5. 5 10. 4 43. 0 72.6 89. 1 48 18. 4 191. 6 78. 9 150 3. 0 3. 32 68. 4 94. 7 31. 8 49--"dist 2. 91 191. 3 80. 4 4. l 1.02 88.6 47.0 8. 2 50--.- 350 we dist 36.6194. 5 79. 7 160 9. 0 16.9 45. 9 63. 7 68. 7 51---- 350 Vls. dist- 16.6191.8 80.0 160 3. 9 6.02 71.6 81. 2 26. 4

The properties of: the naphthenic acids in a semi-pure state obtainedfromthese various distillates, and from 150 vis. bright stock for.comparison, are given in Table IV. The values for Neutralization Numberand molecular weight were obtained from the pure acids. 75

three feet of three-inch, stainless steel pipe packed with one-half-inchBerl saddles was used. The tower had enlarged settling sections at thetop and bottom; The tower was equipped with a extract solution-overflowline; connected to the top, a chargeoil line entering; justbelowrecovered methanol was returned through a cooler to methanolstorage. Extracted acids from the solvent in the methanol recovery towerwere drained directly from the drier reboiler. Sampling lines wereprovided for the rafiinate and extract phases and the recirculatingmethanol stream before and after ammonia addition. A record was kept ofthe oil feed rate, the solvent feed rate, the temperature and pressure,and an exact analysis of the products made as seen in Table V.

NAPHTHENIC ACID EXTRAOTIONPILOT PLANT Charge oil Treating conditionsProducts Run Oil Solvent Sol- Mols Acid No. Acid rate rate, vent/ NH;Temp., Pres- Yield Acid N 0.

Stock No. cc./ ee./ oil per F. sure, of oil No. naph. min. min. ratiomol p. s. i. g. oil acids acid 2. 7 150 30 0. 2 10 140 20 0. 03 2. 7 15015 0. l 10 140 20 95. l 0. 06 2. 7 150 7. 5 0. 05 10 140 30 97. 0. 30 2.7 200 7. 0. 038 140 30 96. 7 O. 45 2. 7 200 100 0. 50 25 140 96. 3 0.033.0 150 15 0.1 9 140 30 95.0 0.55 3. 0 150 30 0. 2 9 140 30 96. 5 0. 402. 9 150 38 0.25 15 150 40 97. 5 0. 14 2. 9 150 100 0. 67 35 150 40 100.3 0.03 2. 9 100 50 0. 5O 30 145 40 97. 0 0. 52 2. 9 100 100 1. 0 50 15015 99. 5 0. 06 2. 9 100 50 0. 50 30 160 40 98. 9 0. 34 2. 9 100 100 1. 0100 160 40 96. 5 0. 28 2. 9 75 150 2. 0 180 160 40 96. 8 0.05 2. 9 125125 1. 0 80 160 40 0. 03 2. 9 125 125 1. 0 50 160 40 0. 03 2. 9 100 500. 50 30 175 40 97. 0 0. 41 2. 9 100 100 1. 0 65 175 40 96. 8 0. 11 1. 6100 25 0. 25 170 97. 8 0. 57 1. 6 100 50 0. 5 10 150 25 97. 9 0. 7O 1. 6100 50 0. 5 10 170 25 97. 2 0. 60 1. 6 100 50 O. 5 170 25 97. 3 0. 48 1.6 100 50 0. 5 30 180 30 0. 1. 6 100 0. 5 10 180 30 0. 1. 6 100 50 0. 510 180 25 99. 7 0. 63 1. 6 100 50 0. 5 14 195 40 0.75 1. G 100 50 0. 523 195 40 0. 52 1. 6 100 100 1. 0 30 170 25 97. 8 0. 38 1. 6 100 100 1.0 170 25 98. 8 1. 6 100 1. 0 170 40 0. 39 1. 6 50 50 1. 0 160 170 40 0.34 1. 6 50 100 2. 0 320 40 0. 23 1. 6 75 2. 0 240 170 40 97. 3 0. 20 1.6 50 100 2. 0 240 170 40 98. 9 0. 29 1. 6 50 100 2. 0 240 170 40 95. 60. 17 1. 5 50 100 2. 0 40 170 40 97. 0 0. 50 1. 5 50 100 2. 0 100 170 4098. 3 0. 23 1. 5 75 150 2. 0 200 170 40 99. 8 0. 17-0. 23

ranged to supply nitrogen to the overflow line, if needed, to maintaintower pressure during transition periods.

The oil to be treated was withdrawn from a charge tank and proceededthrough a metering tank, a rotameter, an electrically heated line and asteam heater to the top of the tower. After passing through the tower,the oil or raflinate was withdrawn from the botton, and pumped by ametering pump through a rotameter to a separate heater and stripper,consisting of a three-inch column containing fifteen inches of openflash-Zone above a five foot section packed with 3/8X5/8 inch Raschigrings, wherein traces of methanol were removed. The stripper was fullyjacketed for l25-pound steam and equipped with additional electricalheat to maintain a temperature of about 320 F. Nitrogen was used as thestripping medium. Methanol was pumped through a metering tank and thecharge heater to the treating tower. The ammonia was passed from acylinder, through a pressure regulator, rotameter and needle valve toenter the methanol line between the methanol rotameter and heater. Afterpassing through the tower, the acid-containing solvent flowed overheadthrough a Grove regulator and a steam heater to an acid recovery towerwhich consisted of ten feet of four-inch stainless pipe, packed with /2x/z inch Raschig rings, and a reboiler. I Ieat was supplied to therecovery tower by steam in the feed heater and reboiler, and throughone-half-inch tubing wound around the column. A temperature of about 270F. was maintained in the reboiler and feed zone. Nitrogen was also usedas the stripping medium in the methanol recovery tower. The

A portion of the treated deasphalted oil from experi ment 74 wasfinished to a 0 F. pour, 90 V1 bright stock by batch phenol extraction,dewaxing with methy ethyl ketone, and clay contacting. A refinedraffiuate, SUS at 210 F, 90 VI and having an acid number of 0.22, adewaxed bright stock, 160 SUS at 210 F., 90 VI, and having an acidnumber of 0.28, and a finished bright stock, 160 SUS at 2l0 F., 90 VI,treated with 10#/bbl. of Filtrol X466, and having an acid number of0.16, were obtained. The phenol extract from this treatment had an acidnumber or 0.85.

As shown in Table V, solvent/oir ratios as low as from 0.1 to 0.2 canreduce the neutralization number of 80 distillate to Well below 0.1. Forthe heavier oil stocks higher solvent/oil ratios are required formaximum acid removal. The ratios required range up to a value of about2.0 for deasphalted oil. The amount of ammonia required for maximum acidremoval depends upon the oil stock being extracted. Runs Nos. 52, 60, 67and 86 show that the amount in terms of mols NH per mol acid ranges froma low of 10 for 80 distillate to a high of 240 for deasphalted oil.

Several related advantages come from the application of the instantprocess to lubricate oils. It is possible to produce marketablenaphthenic acids of relatively high purity in amounts equal to about 2%of the oil treated. There is a pronounced reduction in corrosion in thephenol extraction unit used in conjunction with the naphthenic acidextraction. A sizable reduction in clay treatment requirements forfinishing the lubricating 1 l i stocks to the required neutralizationnumber specifications is gained.

The experiments have shown that the process is particularly applicableto continuous counter-current extraction of' naphthenic acids fromlubricating .oil frac tions. In such counter-current extractionprocesses, when applied to distillate lubricating oils, the invention ispracticed' by treating the oil with a. solvent comprising substantiallyanhydrous methanol and ammonia at a temperature of about 140 to 175 F.using from about 9 to 1'80'mols of ammonia per mol of naphthenic acid inthe oil and a solvent-to-oil ration of about 0.038 to 2.0 andcontinuously separating a rafiinate oil having a reduced naphthenic acidcontent. In applying the technique of continuous; counter-currentsolvent extraction to deasphalted oils from which bright stocks areobtained, the invention is practiced by treating the oil with a solventcomprising substantially anhydrous methanol and ammonia at a temperatureof about 140 to 195 F. using about 10 to 320 mols of ammonia in thesolvent per mol of naphthenic acid in the oil and a solvent-to-oil ratioof about 0.5 to 2.0.

What is claimed is:

1. The process for the extraction of high molecular weight naphthenicacids boiling above about 600 F. from-refined lubricating oils whichcomprises treating of. said lubricating. oils with a solvent consistingof anhydrous methanol containing between about 1 to by weight ofammonia, based on the amount of methanoly at temperatures ranging from80 to 200 F. under pressures of from about atmospheric to 150 12 acid insaid oil ranging from about 9 to 180 and the solvent-to-oil ratios beingfrom about 0.04 to 2.0, and

continuously separating a raifinate oil having a reduced content ofnaphthenic acids.

6. The process in accordance with claim 5 in which the oil being treatedis a refined lubricating oil distillate having a viscosity of about 80SUS at 100 F. and an acid'number of about 2.7.

7. The process in accordance with claim 5 in which the oil being treatedis a refined lubricating oil distillate having a viscosity of about 170SUS at 100 F. and an acid number of about 3.0.

8. The process in accordance with claim 5 in which the .oil beingtreated is a refined lubricating oil distillate having a viscosity ofabout 350 SUS at 100 and an acid number of about 2.9.

9. The process, for the continuous counter-current extraction of highmolecular weight naphthenic acids boiling above about 600 F. fromrefined deasphalted lubricating oils which comprises treating said oilwith a solvent comprising substantially anhydrous methanol and ammoniaat a temperature of about 140 to 195 F., the mols of. ammonia in saidsolvent per mol of naphthenic acid in said oil ranging from about 10 to320 and the solvent-to-oil ratios being from about 0.5 to 2.0 andcontinuously separating a rafi'inate oil having a reduced content ofnaphthenic acids.

10'. The process in' accordance with claim 9 in which the oil beingtreated is a refined deasphalted oil having pounds per'squareinch, andrecovering as the oil phase a lubricating oil substantially devoid ofnaphthenic acids.

2. The .process for the extraction of high molecular weight naphthenicacids boiling above about 600 F. from refined lubricating oils whichcomprises treating said lubricating oils with a solvent consisting. ofmethanol with about 5 to 7% by weight of ammonia and containing not morethan about 0.40% by weight of Water, said amounts of ammonia and waterbeing based on the amount of methanol, said treatment taking place attemperatures ranging from about 140 to 195 F.

and under pressures ranging from about 15 to 40 pounds er square inch,and recoving as the oil phase a lubricating oil substantially devoid ofnaphthenic acids.

3. In the process for the extraction. of high molecular weightnaphthenic acids boiling above about 600 F. from refined lubricatingoils to obtain products substantially devoid of naphthenic acids, theimprovement comprising treating said lubricating oils to solventextraction using low solvent to oil ratios in the order of about 0.2 to2.0'at temperatures of from 140 to 195 F. under pressures of from 15 to40 pounds per square inch, and'employing as the solvent a compositionconsisting of methanol containing between about 5% to 7% of ammonia,based on the amount of said methanol.

4. In the process for the extraction of high molecular weight naphthenicacids boiling above about 600 F. from refined lubricating oils, theimprovement comprising treating said lubricating oils to solventextraction using low solvent to oil ratios in the order of 0.2 to 2.0,temperatures of from 140 to 195 F. under pressures of from 15 to 40pounds per square inch, and employ-- ing as the solvent a compositionconsisting of methanol containing between about 5% to 7% by Weight ofanimonia, no more than about 0.40% by weight of water, said amounts ofammonia and water being based on the amount of methanol.

5. The process for the continuous counter-current extraction of highmolecular weight naphthenic acids boiling above about 600 F. fromrefined distillate lubricating oils which comprises treating said oilwith a solvent comprising substantially anhydrous methanol and ammoniaat a temperature of about 140 to 175 F., the mols of ammonia in saidsolvent per mol of naphthenic an acid number of. about 1.6.

11. The process of removing high molecular weight naphthenic acidsfrom'refined lubricating oil distillates having viscosities at F. offrom about 80 SUS to 170 SUS which comprises treating said distillateswith a solvent consisting of anyhydrous methanol containing betweenabout 5% to 7% by wt. of ammonia, at temperatures ranging; from to F.using pressures of from 15 to 40 pounds per square inch andsolvent-tooil ratio of between about 0.2 to 0.5.

12., In a continuous process for solvent extracting highmolecular-weight naphthenic acids boiling above about 600 F. fromrefined lubricating oils which comprises continuously passing alubricating oil stream into counter-current contact with a solventstream to separate a solvent phase and an oil phase, the improvementcomprising introducing as the solvent a mixture of anyhydrous methanoland ammonia in proportions such that the total solvent-to-oil ratio doesnot exceed about 2.0 and the'mols of ammonia per mol of naphthenic acidpresent in said oil is below 240, said contact taking. place at about140 F. to 190 F. and separatingan oil. phase having a substantiallyreduced acid number and a solvent phase of naphthenic acids.

13. In the process for the continuous counter-current extraction of highmolecular Weight naphthenic acidsabout 10 mols of ammonia per mol ofnaphthtenic acid in said oil are present and recovering as the raifinatean oil having an acid number of about 0.03.

14. In the process for the continuous counter-current; extraction ofhigh molecular weight naphthenic acids" boiling above about 600 F. fromrefined distillate lubricating oils having viscosities of about SUSat;100- F. wherein the oil is contacted with a solvent and. an extractphase and a rafiinate oil phase are continuously separated, theimprovement comprising treating said oil I I with a solvent comprising asubstantially anhydrous mixture of methanol and ammonia, using asolvent-to-oil ratio of about 0.7, at a temperature of about 150 F., andadjusting the amount of ammonia in said solvent so that about mols ofammonia per mol of naphthenic acid in said oil are present andrecovering as the rafiinate an oil having an acid number of about 0.03.

15. In the process for the continuous counter-current extraction of highmolecular weight naphthenic acids boiling above about 600 F. fromrefined distillate lubricating oils having viscosities of about 350 SUSat 100 F. wherein the oil is contacted with a solvent and an extractphase and rafiinate oil phase are continuously separated, theimprovement comprising treating said oils with a solvent comprising asubstantially anyhydrous mixture of methanol and ammonia, using asolvent-tooil ratio of about 1.0, at a temperature of about 160 F., andadjusting the amount of ammonia in said solvent so that about to mols ofammonia per mol of naphthenic acid are present in said oil andrecovering as the ratfinate an oil having an acid number of about 0.03.

16. In the process for the continuous counter-current extraction of highmolecular weight naphthenic acids boiling above about 600 F. fromrefined deasphalted lubricating oils having viscosities of about SUS at210 F. wherein the oil is contacted with a solvent and an extract phaseand a raflinate phase are continuously separated, the improvementcomprising treating said oils with a solvent comprising a substantiallyanyhydrous mixture of methanol and ammonia, using a solvent-tooil ratioof about 2.0, at a temperature of about F., and adjusting the amount ofammonia in said solvent so that about 200 mols of ammonia per mol ofnaphthenic acid in said oil are present and recovering as the rafiinatean oil having an acid number of about 0.17 to 0.23.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Ian. 14, 1926

1. THE PROCESS FOR THE EXTRACTION OF HIGH MOLECULAR WEIGHT NAPHTHENICACIDS BOILING ABOVE ABOUT 600*F. FROM REFINED LUBRICATING OILS WHICHCOMPRISES TREATING OF SAID LUBRICATING OILS WITH A SOLVENT CONSISTING OFANHYDROUS METHANOL CONTAINING BETWEEN ABOUT 1 TO 15% BY WEIGHT OFAMMONIA, BASED ON THE AMOUNT OF METHANOL, AT TEMPERATURES RANGING FROM80* TO 200*F. UNDER PRESSURES OF FROM ABOUT ATMOSPHERIC TO 150